Fibrocystic changes are the most common cause of breast lumps in women ages 30 to 50. Although fibrocystic changes may also be referred to as fibrocystic disease, this is not a disease, but a condition. It can be known as cystic disease, chronic cystic mastitis or mammary dysplasia. This condition is not cancerous. At least 60% of the women in their reproductive years have "lumpy" breasts as a result of these non-cancerous conditions.